This invention relates to a ventilating device and more particularly, to a ventilating suction and exhaust fan device of Plate type in which when exhaustion and suction of air are simultaneously carried out by means of a centrifugal fan, the possibility of mixing of exhaust air and suction air is completely eliminated, as well as the flows of suction air and exhaust air are both converted from centrifugal flows to axial flows.
Recently, many types of ventilators have come into use for ventilating rooms. However, these ventilators, which consist only of axial fans, are not satisfactory. Further, with these ventilators, air is sucked or drawn by reversing the direction of rotation of the fans, and this decreases the efficiency of the ventilators.
In this circumstance, after many experiments and long investigation, the Applicant proposed a ventilating suction and exhaust fan device of Plate type comprising a cylindrical casing, a horizontal partition plate mounted within the casing and extending in a horizontal plane passing through a central axis of the casing and having a rectangular opening formed therein, a cylindrical impeller of Plate type rotatably mounted in the opening of said plate coaxially with respect to the casing, a first shroud or screening plate of semi-circular shape positioned vertically adjacent to rear side of an upper half of the impeller, a second shroud or screening plate of semi-circular shape positioned vertically adjacent to front side of a lower half of the impeller, a first rear vertical partition plate of semi-circular shape positioned adjacent to rear side of the lower half of the impeller and having a semi-circular window of a diameter equal to or slightly smaller than an outer diameter of the impeller, and a second front vertical partition plate of semi-circular shape positioned adjacent to front side of the upper half of the impeller and having a semi-circular window of a diameter equal to or slightly smaller than the outer diameter of the impeller. In this fan device, guide means for converting centrifugal flows generated by the impeller to axial flows. This fan device is disclosed in the Japanese patent publication No. 12939/1976. This fan device is relatively satisfactory in the point that its ventilating efficiency is relatively high. However, in this known fan device, the mixing of exhaust air and suction air can not be completely eliminated, sice the clearances between the shrouds and the end surfaces of the impeller are in communication with the windows of the partition plates through which exhaust air mixes suction air.